Generally, a semiconductor manufacturing device, more particularly a reduction projection exposure apparatus called a stepper is arranged to include driving apparatuses which control to drive respective actuators and a control operation section which generates control commands for the actuators on the basis of numerical information to output them to the driving apparatuses. In such an exposure apparatus, an input power failure in the apparatus power supply voltage due to an instantaneous power interruption or momentary voltage fluctuations called a sag may cause loss of important data, abnormal control operation, abnormal operation of an actuator, or the like.
Conventionally, as a solution to such an input power failure, a method of protecting the entire apparatus with an uninterruptible power supply or a method of incorporating an uninterruptible power supply in the apparatus, thereby issuing a save command or operation stop command to each actuator in accordance with a power supply voltage abnormality time and storing data required to actuate the apparatus again upon recovery has been proposed (e.g., see Japanese Patent Laid-Open No. 6-19520).
Along with recent miniaturization of a semiconductor and an increase in wafer size, an exposure apparatus has been upsized and at the same time has been required to operate at high speed. Additionally, the power consumption of an exposure apparatus has been increasing. For this reason, an uninterruptible power supply to be incorporated in an exposure apparatus in preparation for a power failure need be larger. This causes an increase in footprint and price of the apparatus.
Most recent DC power supplies are switching power supplies. A switching power supply theoretically stands power supply variations, and in many cases, a voltage drop of several ten % does not require backup by an interruptible power supply. Collective backup of a power supply section including such a switching power supply by an uninterruptible power supply is undesirable because it may cause an unnecessary increase in size of the uninterruptible power supply. Since an uninterruptible power supply uses a battery, it needs periodical replacement and may cause an accident such as ignition due to excessive charge and discharge. For this reason, it is preferable not to use an uninterruptible power supply if possible. Even if an uninterruptible power supply is to be used, a small one having a small amount of stored energy is preferably selected.